Time-of-day speed analysis

Sampled-period findings

16th Street & Monon: sampled periods before and after the April 25, 2026 build

Recorded speeds were lower after the build in the sampled weekday mornings, weekday evenings and weekend afternoons. Each retained speed reading receives equal weight. These are comparisons of the periods volunteers sampled; collection windows differ and the data do not isolate the build's effect.

PRE: March 27-April 23, 2026. POST: April 28-May 31, 2026. Times are recorded session labels, treated as Indianapolis local time. There are no individual vehicle timestamps.

Full charts with dates, counts and collection limits

Scroll charts horizontally on small screens, or open an individual chart to zoom.

Source: public speed-study release r2, September 17, 2026. Updated analysis: October 4, 2026. Download period comparisons; read methods and reproduction instructions; download the reproduction script; download verification hashes; download the r2 source package. Link to this analysis.

Methods and reproduction

16th Street and Monon Trail, Indianapolis. Analysis dated October 4, 2026. Source: public speed-study release r2 (September 17, 2026).

PRE March 27-April 23, 2026; POST April 28-May 31, after the April 25 build. Dates are irregular volunteer samples, not continuous monitoring. Session clocks are assumed Indianapolis local time; the source records no explicit timezone. No individual speed reading has a timestamp. AM/PM labels are recorded session fields. Split PM into weekday evenings and weekend afternoons using recorded dates.

8,986 speed readings retained: 3,880 PRE and 5,106 POST. The two r2 flagged POST readings remain excluded; raw rows stay in the source release. Period comparisons exclude 286 PRE readings without a recorded period, so their PRE denominator is 3,594. These counts do not establish distinct vehicle identities. The instrument recorded slower vehicles at a 10 mph floor, according to the existing study notes.

Pool retained readings within each period and phase. Give each reading equal weight. Count above-25 speeds strictly greater than 25; divide by retained n. Quantiles use linear interpolation. An empty session contributes no speed mean.

Collection windows differ. Wednesday AM PRE 08:05-08:30 and POST 08:34-09:34 do not overlap. Other times vary or are ambiguous/missing. Four April 23 PRE PM records overlap; repeated vehicle sampling is unverified. Records are not silently deduplicated. Excluding all April 23 PRE PM records gives 22.5 to 15.8 mph, compared with 21.8 to 15.8 mph when included. This supports the descriptive direction, not an exact causal effect or an assurance of unique vehicle counts.

Alternative weights are supporting mean sensitivities: equal nonempty session, equal date, or equal shared weekday. Within each unit, readings are pooled first. Shared-weekday comparisons change included observations as well as weights and cannot remove confounding. Leave-one-date-out ranges omit one date in one phase at a time; these are sensitivity ranges, not confidence intervals. These checks do not reweight percentiles or threshold shares. No hourly full-day, geographic-point, statistical-significance, injury-risk or causal claim is made.

Reproduce

Download source-r2.zip and speed_time_of_day.py from this folder. Extract the ZIP and pass the folder containing speed_observations_public.csv, survey_sessions_public.csv and release-hashes.json as --release:

python3 speed_time_of_day.py --release PATH_TO_EXTRACTED_RELEASE --output reproduced

Python 3 standard library only. The script verifies every release hash and reconciles all 29 nonempty session summaries with r2 before writing outputs. verification.json records the input and output hashes of the full local analysis package. This website publishes the comparison/coverage/sensitivity CSVs and two charts; the complete local review README and preview are not required to reproduce the numeric results. The linked source package carries the release privacy treatment and license. No respondent identities appear in these derived outputs.